We have carried out investigations relative to regional lymph nodes in patients with cancer and plan to continue such studies. During the past year we extended our previous observations relative to histopathological discriminants of such nodes. In one study we compared the prognostic significance of lymph nodes involved with tumor which was contained within the confines of the nodal capsule with those in which the tumor extended through the latter structure into surrounding fat. Preliminary evidence indicates that extranodal extension may carry a worse prognosis. Another study evaluated the prognostic significance of regional lymph node histology other than sinus histiocytosis. A correlation was made between LN patterns considered to reflect immunologic function and 31 other histologic and 8 clinical features. Findings failed to demonstrate value for such nodal assessments. Finally, information was obtained from 151 RLNs obtained from women with breast cancer. The effect of RLNCs on macrophage migration was ascertained. Such nodes were found to elaborate MIF (macrophage inhibitory factor). The degree of inhibition varied from node to node in the same patient and was found to be less when RLNCs were from positive node patients. This was absent when RLNCs came from nodes containing tumor. Studies for the coming year will primarily relate to macrophage content of nodes and their relationship to peripheral blood monocytes. BIBLIOGRAPHIC REFERENCES: Pathologic Findings from the National Surgical Adjuvant Breast Project (Protocol No. 4) II. The Significance of Regional Node Histology other than Sinus Histiocytosis in Invasive Mammary Cancer. Fisher, E.R.; Gregorio, R.; Redmond, C.; Dekker, A.; Fisher, B. Am J. Clin Path, 65: 21-30, 1976. Pathologic Findings from the National Surgical Adjuvant Breast Project (Protocol No. 4) III. The Significance of Extranodal Extension of Axillary Metastases. Fisher, E.R.; Gregorio, R.; Redmond, C.; Kim, W.S.; Fisher, B. Am Clin Path 65: 439-44, 1976.